During the last decade, numerous processes and procedures have been developed for genetically engineering cells in order to produce a wide variety of proteins and glycoproteins. These procedures involve utilizing recombinant DNA technology to prepare a vector which includes genetic material that codes for a specific protein or glycoprotein. Upon introduction of the vector into the host cell, the inserted genetic material instructs the host cell's biochemical machinery to manufacture a specific protein or glycoprotein.
Glycoproteins are proteins having carbohydrate groups attached at various points along the protein's amino acid backbone. The carbohydrate groups are commonly attached to asparagine, serine or threonine. The genetic sequence introduced into the host cell usually includes instructions with respect to the amino acid sequence of the protein and the location and structure of the carbohydrate groups. Most of the cell lines which are commonly used as host cells are capable of following the vector's instructions with respect to preparing a protein having a specific amino acid sequence. However, many host cells are not capable of following instructions with respect to glycosylation of the protein. For example, lepidopteran insect cells are a common host cell used in producing a wide variety of proteins in a baculovirus system. However, such lepidopteran cells do not contain all of the cellular glycosylation machinery present in mammalian cells required to attach certain carbohydrate groups to the proteins it manufactures.
From the above, it is apparent that there is a need to identify human polypeptides which can be used to alter the glycosylation machinery of non-human host cells in order to control the structure of carbohydrates attached during glycosylation. Such a process for controlling host cell glycosylation would be useful not only in expressing glycoproteins which accurately mimic naturally occurring proteins, but would also be useful in preparing glycoproteins having selected altered carbohydrate structures for diagnostic and research uses.